Audio Reproducing Apparatus And Audio Reproducing Method, Allowing Efficient Data Selection

ABSTRACT

In a music selection mode, a reproduction object deciding unit in an audio reproducing apparatus selects a plurality of pieces of candidate music from music data stored in a storage unit and has a reproducing unit reproduce them simultaneously. An assigned position deciding unit controls an audio processing unit in such a manner as to assign the sound images of the pieces of candidate music respectively to different positions. An input by which one unit of sound is selected from among a plurality of sounds that a user hears from the different positions is entered to an input unit. Then the reproduction object deciding unit determines that music data corresponding to the sound has been selected. This causes a changeover to a normal mode and the selected music data only is reproduced.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an audio reproducing technology and, inparticular, to an audio reproducing apparatus for reproducing one unitof audio data selected from a plurality of audio data and an audioreproducing method applied thereto.

2. Description of the Related Art

As technological developments surrounding audio data, there are theadvancement of coding techniques, the arrival of larger-capacity andsmaller-size storage devices, and the diversification of dataacquisition routes. With these as the technological background, thenumber of audio data, such as music contents, possessed by individualsare increasing at an accelerated pace. At the same time, there arediversifying environments for the reproduction of audio data. Forexample, people can readily enjoy the realistic sensation created by a“5.1-channel surround system” or listen to a variety of music whereverthey are from a portable audio player that stores a large volume ofdata.

When a desired piece of music among audio data in the user's possessionis to be reproduced, the selection is normally done using characterinformation such as an album name or a song title. However, if suchaudio data come in a large number, it is increasingly difficult to finda desired song title or the like. For example, when a large volume ofaudio data are stored in a portable audio player, a display provided insmall equipment may have a problem of a limited number of characters itcan display at a time. As a result, it may call for complicatedoperations such as scrolling a screen, deciphering, and selectingcharacters until desired data are reached.

Moreover, portable audio reproducing apparatuses, such as portable audioplayers and car stereos, are often used by persons during walking, in arunning vehicle or in such other circumstances that do not allow them toeasily read the characters displayed on a display. This further adds tothe troublesomeness the user feels about the operation of selecting asong or piece of his or her choice.

SUMMARY OF THE INVENTION

The present invention has been made in view of the foregoing problems,and a general purpose thereof is to provide a technology that makesselection of a piece of audio data from a plurality of audio dataeasier.

An audio reproducing apparatus according to one embodiment of thepresent invention relates to an audio reproducing apparatus. This audioreproducing apparatus, which has an interface capable of having a userselect any one of a plurality of audio data, includes: a reproducingunit which assigns sound images of a plurality of audio signalsreproduced from a plurality of candidate audio data to different spatialpositions around a user, and outputs the plurality of audio signalssimultaneously; and an input unit which specifies a selected audio databy having the user select one of a plurality of outputted sounds thatthe user hears simultaneously from different directions.

The “audio data” as used herein may be any data of recorded sound, suchas music data, voice data, radio programs and music contents and mayalso be a set of audio data composed of minimum units thereof, such asan album that contains a plurality of recorded pieces of music.

Another embodiment of the present invention relates to an audioreproducing method. This audio reproducing method includes: outputting aplurality of audio signals simultaneously reproduced from a plurality ofcandidate audio data, after assigning sound images of the plurality ofaudio signals to different spatial positions around a user; receiving aninput by which the user selects one of a plurality of outputted soundsthat the user hears simultaneously from different directions; andreproducing only audio data corresponding to the selected one unit ofsound.

Optional combinations of the aforementioned constituting elements, andimplementations of the invention in the form of methods, apparatuses,systems, and computer programs may also be practiced as additional modesof the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustration for describing in outline an audio reproducingapparatus according to the present embodiment.

FIG. 2 illustrates a structure of an audio reproducing system thatincludes an audio reproducing apparatus according to the presentembodiment.

FIG. 3 illustrates a detailed structure of an audio processing unitaccording to the present embodiment when it performs a preprocessing oran aural segregation processing of audio signals.

FIG. 4 illustrates a concrete example of positions to which the soundimages of a plurality of music data are assigned in a music selectionmode of the present embodiment.

FIG. 5 is a front view of a controller as an example of an input unit inthe present embodiment.

FIG. 6 is a flowchart showing an operation procedure of an audioreproducing apparatus according to the present embodiment.

FIG. 7 is a front view of a controller which is another example of theinput unit in the present embodiment.

FIG. 8 illustrates a configuration of a pair of earphones, which servesalso as an input unit, according to the present embodiment.

FIG. 9 is a front view of a controller, which serves also as a displayunit, according to the present embodiment.

FIG. 10 illustrates an example of classification structure of musicutilizable in the present embodiment.

FIG. 11 is a flowchart showing an operation procedure of an audioreproducing apparatus when the selection method by music classificationis employed in the present embodiment.

DETAILED DESCRIPTION OF THE INVENTION

The invention will now be described by reference to the preferredembodiments. This does not intend to limit the scope of the presentinvention, but to exemplify the invention.

FIG. 1 is an illustration for describing in outline an audio reproducingapparatus according to the present embodiment. The audio reproducingapparatus 16 according to the present embodiment reproduces audio datastored in a storage unit 12 and outputs the audio signals thus obtainedto a user 50 through an output unit 30. The audio data in the followingdescription is assumed to be music data, but this does not intend tolimit the scope of this invention. Rather, the audio data may be anysound data, such as voices in a comic storytelling or a conference,sounds in a program, environmental sounds, and voices on broadcastwaves.

When a user 50 tries to select a piece of music, the audio reproducingapparatus 16 acquires a plurality of candidate music data from thestorage unit 12 and outputs them by simultaneously reproducing them. Atthis time, sound images of audio signals corresponding to the respectivemusic data are assigned to different positions. In a simplestarrangement, two music data are reproduced as candidates, and one audiosignal (arrow 52) is sent to the right ear of the user 50, and the otheraudio signal (arrow 54) to the left ear. In FIG. 1, a pair of earphonesis used as the output unit 30, for ease of understanding, but thisshould not be considered as limiting. The output unit may also be aplurality of speakers or the like. Hereinbelow, a plurality of candidatemusic data and audio signals outputted by reproducing them arecollectively referred to as “candidate pieces of music”. On the otherhand, the music data stored in the storage unit 12 may not necessarilybe in individual pieces of music, but may also be in sets of multiplepieces of music, such as albums. Also, when the audio reproducingapparatus 16 is simultaneously reproducing the candidate pieces of musicfrom which the user selects one as described above, the audioreproducing apparatus 16 is said to be in a “music selection mode”.

The user performs a music selection by selecting one from the candidatepieces of music which he/she listens simultaneously. Hereinbelow, themusic data of a selected piece of music and the audio signal outputtedby reproducing it are collectively referred to as a “selected piece ofmusic”. Once a selected piece of music is determined, the audioreproducing apparatus 16 switches the music selection mode to a normalmode in which the selected piece of music only is reproduced. Or,without leaving the music selection mode, the audio reproducingapparatus 16 carries out further reproduction of candidate pieces ofmusic related to the selected piece of music. For example, when a pieceof music is to be selected from the tracks in an album, selection ofeither one of the pieces the user hears from the right and left may setoff switch of candidate pieces of music in the recorded order or in thereverse order thereof. When three or more candidate pieces of music areto be reproduced, all the sound images of pieces are assigned todifferent positions. For example, all the sound images of tracks in analbum may be assigned to their respective positions, from which theirrespective sounds reach the user simultaneously.

By selecting one out of the candidate pieces of music he/she listenssimultaneously, the user may narrow the candidate pieces of music or mayfinally determine a selected piece of music. By this feature, the usercan select music without looking at the display, and the efficiency inmusic selection is distinctly improved compared with the case where theuser checks data one by one by looking at the characters. Further, theuser selects music while he/she is listening to actual pieces of music,so that the music selection can be made even when the user has only avague memory of the song title or the like. Moreover, even when the userhas no clear idea about a specific piece of music he/she wants to listento, a “zapping” of pieces of music can be made effectively on suchoccasions as when the user feels like listening to music fitting themood of the moment or when he/she wants to check on the whole range ofmusic he/she has recorded in the past.

FIG. 2 illustrates a structure of an audio reproducing system thatincludes an audio reproducing apparatus 16 according to the presentembodiment. The audio reproducing system 10 includes a storage unit 12,an audio reproducing apparatus 16, an output unit 30, and a display unit22. The storage unit 12 stores a plurality of music data. The audioreproducing apparatus 16 reproduces candidate pieces of music, assignsthe sound images of them to different positions, and then outputs themas mixed audio signals in the music selection mode. The output unit 30outputs the audio signals as sounds. The display unit 22 visuallydisplays the information on the pieces of music currently beingreproduced. It is to be noted, however, that the display unit 22 is notan essential element of the present embodiment which permits musicselection without the use of visual information. Also, since the audioreproducing apparatus 16 reproduces a piece of music, in the normalmode, in the same way as an ordinary audio player, emphasis in thefollowing description will be placed mainly on the operation thereof inthe music selection mode.

The audio reproducing system 10 may be structured with integrally orlocally connections like a personal computer, a music reproducingapparatus such as a portable player, or the like. In such anarrangement, a hard disk or flash memory can be used as the storage unit12, a processor unit as the audio reproducing apparatus 16, and built-inspeakers, an externally connected speakers, earphones or the like as theoutput unit 30. Also, as the storage unit 12, a hard disk or the likewithin a server connected to the audio reproducing apparatus 16 via anetwork may be used. The music data to be stored in the storage unit 12may be encoded in a commonly used coding format such as MP3.

The audio reproducing apparatus 16 includes an input unit 18,reproducing units 14, an audio processing unit 24, a down mixer 26, anda control unit 20. The input unit 18 receives an instruction input aboutmusic selection from the user. The reproducing units 14 outputs audiosignals by decoding music data The audio processing unit 24 performssound processing, including assignment of individual sound images ofaudio signals to their respective positions in the music selection mode.The down mixer 26 generates an output signal having a desired number ofchannels by mixing the processed audio signals. The control unit 20controls the operation of the reproducing units 14 and the audioprocessing unit 24 and the display of the display unit 22 by determiningmusic data to be reproduced and positions to which their sound imagesare assigned.

The input unit 18 provides an interface by which the user changes thepositions to which the sound images of candidate pieces of music areassigned or selects a piece of music in the music selection mode. Theinput unit 18 may simply be an ordinary controller with operation keys.However, the audio reproducing apparatus 16 according to the presentembodiment is capable of music selection by a much simpler operation,and hence it is desirable that the input unit 18 be constituted by somedevice that can be operated by the user's feeling inside his/her pocketor bag, for instance. Concrete examples will be discussed later.

The control unit 20 includes a reproduction object deciding unit 28 andan assigned position deciding unit 29. The reproduction object decidingunit 28 decides candidate pieces of music to be reproducedsimultaneously in the music selection mode or a selected piece of musicto be reproduced in the normal mode based on an instruction input fromthe user and communicates the decision to the reproducing units 14. Theassigned position deciding unit 29 decides the positions to which thesound images of individual candidate pieces of music are assigned in themusic selection mode, and updates the positions if so instructed by theuser, and communicates the setting to the audio processing unit 24. Ifnecessary, the control unit 20 also performs a control of the displayunit 22 such that it displays an image or the like symbolizing the pieceof music being reproduced.

The reproducing units 14 read out candidate pieces of music or aselected piece of music decided by the reproduction object deciding unit28 of the control unit 20 from among the music data stored in thestorage unit 12, and generate audio signals by decoding them. FIG. 2shows four reproducing units on an assumption that there are four musicdata that can be reproduced simultaneously, but this only intends toexemplify the embodiment and the number of reproducing units is notlimited to the four. Also, where parallel processing of reproduction canbe performed by a multiprocessor or the like, the reproducing units 14may have an appearance of a single unit. In FIG. 2, however, thereproducing units 14 are shown as separate processing units forreproducing individual music data and generating their respective audiosignals. In the normal mode, any one of the reproducing units 14 decodesa selected piece of music.

The audio processing unit 24 carries out a processing in which the soundimages of a plurality of audio signals decoded are assigned to theirrespective positions which have been decided by the assigned positiondeciding unit 29 of the control unit 20, in the music selection mode. Inaddition to this, the audio processing unit 24 may, as appropriate,perform preprocessing, such as gain adjustment or monauralization of aplurality of audio signals, or an aural segregation processing to havethe user more easily perceive the reproduced candidate pieces of musicfrom each other auditorily from the viewpoint other than the sound imagelocalization. The details of such arrangements will be described later.

The down mixer 26 mixes a plurality of inputted audio signals aftermaking various adjustments to them if required and outputs them as anoutput signal having a predetermined number of channels, such asmonaural, stereo, and 5.1-channel. The number of channels may be fixed,or it may be such that the user can switch them by hardwarewise orsoftwarewise. The down mixer 26 may be constituted by an ordinary downmixer.

FIG. 3 shows a detailed structure of an audio processing unit 24 when itperforms a preprocessing or an aural segregation processing on audiosignals. The audio processing unit 24 includes a preprocessing unit 40,an aural segregation filter 44, and a localization-setting filter 46.The preprocessing unit 40 performs gain adjustment so that the pluralityof audio signals may become equal in effective amplitude or turns theindividual audio signals into a monaural signal. In addition to this,the preprocessing unit 40 may carry out, as appropriate, any necessaryprocessing other than the aural segregation processing or thelocalization setting processing. The preprocessing unit 40 can berealized by the use of an ordinary auto gain controller, converter orthe like.

The aural segregation filter 44 performs processing on at least any oneof a plurality of audio signals such that they can be perceivedseparately from each other. In FIG. 3, the aural segregation filter 44is represented by a single block, but it may be constituted by aplurality of filters. For example, it may be any of frequency-banddivision filters, time-division filters, modulation filters, andprocessing filters, as described in the following or a combinationthereof.

The frequency-band division filter divides the audible band offrequencies into a plurality of blocks and assigns each block to atleast one of a plurality of audio signals. It then extracts only thefrequency components belonging to the assigned blocks from each audiosignal. For example, if the setting is such that the boundary frequencyof each block is any of the boundary frequencies of the 24 criticalbands of Bark's scale, then there will be less likelihood of a frequencycomponent of an audio signal masking the frequency component of anotheraudio signal. This arrangement facilitates auditory segregation in theinner ear.

The time-division filter changes the amplitude of audio signals at acommon period such that peaks thereof occur at different times. That is,a time slot is allotted to each of the plurality of audio signals. Theperiod is to be on the order of several tens to several hundreds ofmilliseconds. This will make it easier for the user to perceive anaurally separation by the temporal resolution ability of the inner ear.

The modulation filter causes a specific change periodically in all orany of the audio signals. For instance, it may carry out a modulation ofthe amplitude of the audio signals or a modulation of the frequencycharacteristics thereof. The modulation may be applied in pulses in ashort period of time or changing gradually over a long time of severalseconds. When a common modulation is applied to a plurality of audiosignals, the peak timing is varied for each audio signal. Or thearrangement may be such that noise, such as clicks, is addedperiodically, processing practicable by an ordinary audio filter isapplied or the position of the sound image is swung right and left.Thus, the user is given clues for noticing the auditory streams of audiosignals by a combination of above-mentioned modulations, differentmodulations applied to different audio signals or staggered timing foraudio signals.

The processing filter performs a processing constantly on all or any ofthe audio signals. The processing may be one or a combination of avariety of acoustic processings practicable by an ordinary effecter,such as echoing, reverbing and pitch-shifting. The arrangement may besuch that the frequency characteristics are constantly changed fromthose of the original audio signals. When the processing is performed ona plurality of audio signals, the kind or degree of the processing mustalways be varied for each audio signal.

A plurality of audio signals outputted from the preprocessing unit 40are thus inputted to filters such as described above, and as a result, aplurality of processed audio signals are outputted from the auralsegregation filter 44. The control unit 20 performs controls concerningwhich of the plurality of audio signals are to be inputted to whichfilters or what processings are to be effected within the filters, bymaking necessary settings for the respective filters based on thepositions assigned for the respective audio signals and so forth.

The control unit 20 may set one or more filters in such a manner thatthe aural perceivability level changes depending on the assignedpositions. For that purpose, the audio signals that is to be with a highperceivability may be given wider frequency bands by a frequency-banddivision filter or more time by a time-division filter. Or the soundvolume may be simply varied. For example, in an embodiment in which thesound image of a desired piece of music is shifted to the front and thenselected finally as will be discussed later, the assigning of the soundimage of an audio signal to the front position so that it can be heardmore distinctly than the others makes it easier for the user to decidewhether to select it or not.

It is to be noted that whether to perform aural segregation processingor not or how far it is to be realized by the use of the above-mentionedfilter or filters constituting the aural segregation filter 44 may bedetermined as appropriate in consideration of the processing capacity ofthe processor constituting the audio processing unit 24, the clarity ofactual audio signals or the necessity for aural segregation. Thelocalization-setting filter 46 assigns sound images of audio signals totheir respective positions, using a commonly used technique.

FIG. 4 illustrates a concrete example of positions to which sound imagesof a plurality of music data are assigned in the music selection mode.In this example, four candidate pieces of music can be reproducedsimultaneously, and their sound images are assigned to the left, front,right, and back positions of the user 50, respectively. In cases wheremusic data of four albums are stored in the storage unit 12 or wherecandidate pieces of music have been narrowed down to four pieces byinstruction input from the user up to the moment, the reproductionobject deciding unit 28 decides the pieces of music each recorded in thefirst track of the four albums or the four narrowed-down pieces of musicas the candidate pieces of music.

And the assigned position deciding unit 29 performs such control as toassign the sound images of the four candidate pieces of music 68, 62,64, and 66 to the left, front, right and back positions, respectively.As a result, the user 50 listens the different pieces of music comingfrom the left, front, right and back positions simultaneously. At thispoint, if the user 50 enters an instruction input to shift the assignedpositions for the sound images of the pieces of music clockwise(hereinafter referred to as “shift music forward” also) via the inputunit 18, the assigned position deciding unit 29 updates the assignedpositions such that the sound image of the candidate piece of music 68shifts from left to front (arrow 69 a), that of the candidate piece ofmusic 62 from front to right (arrow 69 b), that of the candidate pieceof music 64 from right to back (arrow 69 c), and that of the candidatepiece of music 66 from back to left (arrow 69 d). As the audioprocessing unit 24 assigns the sound images to the updated positions bysetting the localization-setting filter 46 to reflect the update, theuser 50 feels that the four candidate pieces of music have turned 90degrees around him/her.

By repeating this operation, the user 50 can rotate the sound images ofthe four candidate pieces of music until they come from desiredpositions. When he/she has decided on his/her choice by listening to thefour candidate pieces of music simultaneously, the user 50 “shifts themusic forward” so that the chosen piece of music can be heard fromfront. And as a selection is entered via the input unit 18, the chosenpiece of music is determined as the final selection. After this, themode shifts to the normal mode, and the reproduction object decidingunit 28 performs control such that the selected piece of music only isreproduced. Thus, according to the present embodiment, the user canselect a piece of music simply by “shift music forward” operation and“select finally” operation while listening to candidate pieces of musicbeing reproduced simultaneously. In this music selection process, theuser hears multiple pieces of music simultaneously and therefore he/shehas greater freedom of choice than the selection of music with anordinary audio player in which he/she has to reproduce individual piecesof music one by one. That is, the user can select a piece of music moreefficiently and almost as if he/she is looking at a list of song titlesor the like. This can be done without actually looking at the list.

Although FIG. 4 has employed four positions for assignment for ease ofunderstanding, the efficiency in music selection may be further raisedby increasing the number of positions. For instance, even when tenalbums are stored in the storage unit 12, an album selection may be madein the same way as described above by assigning them to ten positions.In the present embodiment, the assigned positions are a means by whichthe user 50 is given a sense that he/she is shifting a desired piece ofmusic to the front, so that there is no great necessity for the user toclearly distinguish the sounds coming from positions other than thefront or its neighboring positions. Hence, when there are many candidatepieces of music, it is not necessary that the assigned positions bearranged at equal intervals. For example, the assigned positions may bearranged closer together in the back area of the user 50 and wider apartin the front area. Also, for the same reason, a plurality of music datamay be assigned to a single position in the back of the user 50.

In a case where there are a larger number of candidate pieces of musicthan the number of positions for assignment, one candidate piece ofmusic may be replaced by another at each shifting unlike the case ofFIG. 4 in which the same pieces of music are rotated. For example, inFIG. 4, the shifting of arrow 69 d is eliminated, and instead thecandidate piece of music 66 having been assigned to the back position isexcluded from the objects of reproduction at an instruction input of“shift music forward”. And a new candidate piece of music is assigned tothe left position. In this case, too, the user can select a piece ofmusic simply by “shift music forward” operation and “select finally”operation while listening to the candidate pieces of music. Also,because of the feature of simultaneous hearing of a plurality ofcandidate pieces of music, the efficiency in music selection, even whenthere are only two assigned positions, for example, right and left, willbe nearly twice as high as an ordinary selection process in which theuser listens to candidate pieces of music one by one. And it goeswithout saying that the more the assigned positions, the higher theselection efficiency will be.

In the example of FIG. 4, the assigned positions are arranged circularwith the user 50 in the center, but their arrangement may be in otherfigures. For example, they may be arranged on the sides of a quadrangleor on straight lines. Furthermore, they may be arranged above and belowthe user, or on a spherical surface, a cubic surface or the like. Also,the position where the user finally selects a piece of music does nothave to be the front, but it may be set at any position by reminding theuser of it beforehand. In other words, the arrangement of assignedpositions and the destination to which a piece of music to be selectedis shifted may be optionally determined as long as such positions cangive the user an impression that he/she is moving a desired piece ofmusic closer to the destination by operating the input unit 18.

Also, such positions may be so arranged as to meet the tastes of theuser. For example, where an audio reproducing apparatus is to beoperated in the user's own room, the positions may be assigned such thatthey correspond to the positions of various objects placed in the room.Information concerning the positions to be assigned is to be stored in amemory (not-shown) that the assigned position deciding unit 29 canaccess for reference when it assigns sound images of candidate pieces ofmusic to them.

FIG. 5 is a front view of a controller, as an example of the input unit18, which realizes the operation of an audio reproducing apparatus 16 asdescribed hereinabove. The controller 70 may be housed in a separateenclosure connected to the body of an audio reproducing apparatus 16 ormay be installed directly on the surface of the body of an audioreproducing apparatus 16. When a separate enclosure is used, theconnection may be wired or wireless. The controller 70 includes a “NEXT”button 18 a and an “ENTER” button 18 b. The “NEXT” button 18 a is abutton for entering an instruction input of “shift music forward” bywhich the positions assigned for candidate pieces of music are shifted,and the “ENTER” button 18 b is a button for entering an instructioninput of “select finally” by which the candidate piece of music assignedto the front is finally determined as the selected piece of music.

As described hereinabove, music selection according to this embodimentdoes not rely on visual information, so that the operation for selectinga piece of music can be performed with these two buttons. With the inputunit 18 structured as simple as this, the user can carry a controller 70inside a coat or trouser pocket and select music by touch. Moreover,since the operation itself is simple, the user can select music whiledoing something else.

It should be understood that variations of instruction inputs may befurther increased by the way the buttons of the controller 70 arepressed or according to the conditions when they are pressed. Forexample, the arrangement may be such that pressing the “NEXT” button 18a in the normal mode causes a changeover to the music selection mode orthat pressing the “NEXT” button 18 a twice in succession in the musicselection mode reverses the direction of shifting music.

Now a description will be given of an operation of an audio reproducingapparatus 16 realized by a structure as described so far. FIG. 6 is aflowchart showing an operation procedure of the audio reproducingapparatus 16. First the reproduction object deciding unit 28 detects asign that indicates the user's desire to select music (Y of S10). Morespecifically, a detection is made when the audio reproducing apparatus16 has started operating or when the user has entered an instructioninput to that effect to the input unit 18. Thereupon, the reproductionobject deciding unit 28 decides a plurality of music data as candidatepieces of music, and the assigned position deciding unit 29 decides thepositions to which the sound images of the candidate pieces of music areassigned, respectively (S12). Information on the candidate pieces ofmusic is given to the reproducing units 14, and information on thepositions to which they are assigned is given to the audio processingunit 24.

The candidate pieces of music to be decided by the reproduction objectdeciding unit 28 may be selected in an order of storage by the storageunit 12 or in some other sequence such as an order sorted by album,music title or performer. Also, candidate pieces of music that have somerelevance to the pieces of music reproduced just before may be extractedthrough analysis of various information provided by the pieces of musicreproduced just before. For example, selection may be made one by onefrom a group of music having some relevance, such as the pieces of musicplayed by the same performer as one of the pieces of music reproducedjust before, those played by similar performers, those belonging to thesame genre or those having completely opposite characteristics. Thepieces of music reproduced just before may be included among thecandidate pieces of music.

Next, the reproducing units 14, the audio processing unit 24 and thedown mixer 26 output the candidate pieces of music decided by thereproduction object deciding unit 28 by reproducing them simultaneouslyand assigning their sound images to positions decided by the assignedposition deciding unit 29 (S14) The user listens to the sounds outputtedfrom the output unit 30. When the user gives an instruction of “shiftmusic forward” to the input unit 18 (Y of S16), the assigned positiondeciding unit 29 updates the positions to which the sound images of thecandidate pieces of music are assigned by shifting the assignedpositions by one position each (S18).

The user shifts a desired piece of music to the front or any otherpredetermined position by repeating the instruction input of “shiftmusic forward” and then selects it as the selected piece of musicfinally. When an instruction input indicating a final music selection isentered (Y of S20), the reproduction object deciding unit 28 givesinformation on the selected piece of music to a reproducing unit 14 andthe reproducing unit 14 starts reproducing the selected piece of musiconly (S22). At this time, there is only one piece of music that isreproduced, so that the audio processing unit 24 and the down mixer 26may be stopped or part of them may be operated as required. Without aninstruction input of “shift music forward” or final music selection (Nof S16, N of S20), the reproduction of candidate pieces of music is kepton in the same condition (S14).

Through the operation as described above, the user can select a desiredpiece of music from among multiple pieces of music and reproduce it. Andif the user enters an instruction input indicating a desire to doanother music selection, for instance, while listening to a selectedpiece of music, then the music selection mode will be turned on and aprocessing as described above will be carried out (Y of S10, S12 toS20). Or if he/she does not, the user can keep listening to the piecesof music in turn from the selected piece in the normal mode (N of S10,S22).

Now a description will be given of another example of the input unit 18that can realize the operation of the audio reproducing apparatus 16 ina similar manner. FIG. 7 is a front view of a controller that has astructure different from that of FIG. 5. As with the controller 70 shownin FIG. 5, the controller 72 may be installed directly on the body of anaudio reproducing apparatus 16 or may be housed in a separate enclosureThe controller 72 includes four direction pointing buttons 18 c, 18 d,18 e and 18 f and a music shift button 18 g.

With the controller 70 shown in FIG. 5, the user shifts the assignedpositions of sound images so that he/she can hear a desired piece ofmusic from front, and then selects it finally as the selected piece ofmusic. With the controller 72 introduced, on the other hand, the usercan select one of the four candidate pieces of music coming from fourdirections by pressing the relevant one of the direction pointingbuttons 18 c, 18 d, 18 e and 18 f. The number of the direction pointingbuttons is not limited to four, but it may be increased or decreasedaccording to the number of positions to which sound images are assigned.However, it is desirable that the number thereof be such that the usercan select a piece of music by distinguishing the directions of all theassigned pieces of music. And when a selection is to be made from manycandidate pieces of music, the process is made by the replacement ofcandidate pieces of music, which is effected by the pressing of themusic shift button 18 g to shift the assigned positions of sound images.

Next, as another example of the input unit 18, a description will begiven of a mode in which input is made by a method other than buttonoperation. FIG. 8 illustrates an arrangement in which a pair ofearphones serves also as an input unit 18. The earphones 74 are providedwith an acceleration sensor 76 in the part fitted to each ear. Andtogether with a direction deciding unit 78 provided in the body of anaudio reproducing apparatus 16, it constitutes an input unit 18. In thisarrangement, the direction the user's face turns to is detected, and thecandidate piece of music assigned to this direction is selected as theselected piece of music. Although earphones are illustrated in FIG. 8,they, in the following description, may be replaced with a headphone orany other device which the user puts on to listen to music. Also, theacceleration sensor 76, in the following description, may be any sensorcoming with a gyrosensor or the like, as long as it can detect any ofthe acceleration, angular velocity, displacement and the like of anobject. In what is to follow, such a sensor is the acceleration sensor76.

The earphones 74 not only output audio signals received from the downmixer 26 through a cable 80 but also detect the acceleration of theuser's head with the earphones 74 on by the operation of theacceleration sensor 76. Information on the detected acceleration iscommunicated to the direction deciding unit 78 via the cable 80. Thedirection deciding unit 78 calculates the orientation of the user's facebased on the acquired information on the detected acceleration. Notethat existing technology may be employed as a technique for calculatingthe orientation of the user's face from the acceleration.

In the music selection mode, the reproduction object deciding unit 28 ofthe control unit 20 decides the candidate piece of music assigned to theposition corresponding to the direction the user is facing as theselected piece of music from among a plurality of candidate pieces ofmusic. In this manner, the user can select a piece of music simply byturning his/her face in the direction from which he/she hears a desiredpiece of music. This mode of operation may be only possible in thepresent embodiment which associates music with the direction from whichit can be heard. The more the objects, such as a display or controller,that are present between music data and the movement of the user, thegreater the troublesomeness of operation the user feels and thepossibilities of operation error will be. With input given through theearphones 74, the user can select music simply by turning his/her facein the direction from which a desired piece of music is coming.Therefore, there is a direct connection between music data and themovement of the user, and consequently there will be fewer operationerrors because of the great affinity of the human interface.

When the positions to which sound images of candidate pieces of musicare assigned correspond to the positions of various objects placed inthe user's own room as described earlier, the user can derive a kind ofamusement from a feature that a piece of music assigned to the positionof an object is selected when the user turns his/her face toward theobject.

Note that the present embodiment may also be carried out without thecable 80 if the transmission and reception of data between the earphones74 and the audio reproducing apparatus 16 are performed wirelessly usingradio waves or such other existing technology. Also, the accelerationsensor 76 may be worn on a part of the body of the user instead offitted on the earphones or headphone. This way, an optimum input methodcan be selected according to the environment the user is in or anyphysical handicap he/she may have. Further, the input unit 18 may beconstituted by a combination of earphones 74 fitted with an accelerationsensor 76 and a controller as shown in FIG. 5 or FIG. 7. For example,the arrangement may be such that simply turning toward the direction inwhich the user hears a desired piece of music does not select the music,but it can be finally selected only when a final selection button ispressed. In this case, too, necessary operation via the button islimited, and music selection can be done quite easily.

Next, a description will be given of an example in which an input unit18 and an output unit 30 are integrated in a single structure. FIG. 9 isa front view of a controller which serves also as a display unit. Acontroller 90 includes a display screen 22 a, a “NEXT” button 18 a andan “ENTER” button 18 b The functions of the “NEXT” button 18 a and the“ENTER” button 18 b are the same as those of the “NEXT” button 18 a andthe “ENTER” button 18 b of the controller 70 shown in FIG. 5. Thecontroller 90 displays an image symbolizing a piece of music beingreproduced on the display screen 22 a. An image symbolizing music datamay be an image from an album jacket, a frame from a promotion video, amoving image of a promotion video, an image of the sender of music databeing played, or simply a title or such other character informationturned into image data.

In the music selection mode, all images symbolizing candidate pieces ofmusic being reproduced simultaneously are displayed on the displayscreen 22 a. At this time, the images displayed are so arranged as toreflect the positions to which the respective pieces of music areassigned. In the example of FIG. 9, it is assumed that the user islistening to four candidate pieces of music of which sound images isassigned to the left, front, right and back positions, and thus theimages symbolizing them are being displayed in the left (92 a), top (92b), right (92 c) and bottom (92 d) positions, respectively, on thedisplay screen 22 a. When an instruction input of “shift music forward”is entered through the “NEXT” button 18 a, the control unit 20 updatesthe assigned positions of the sound images and at the same time changesthe arrangement of the images on the display screen 22 a in such amanner as to reflect the updated positions. When a piece of music isfinally selected through the “ENTER” button 18 b, the normal mode is setand the image symbolizing the selected piece of music only is displayed.

In an embodiment like this, if the user can check the display screen 22a, the user can visually confirm which pieces of music are coming fromwhich directions in the music selection mode. This confirmation of musiccan be obtained very efficiently because a plurality of music data canbe checked visually at once. Also, the display of images in anarrangement reflecting the assigned positions of sound images allows theuser to get an intuitive grasp.

With an audio reproducing apparatus thus far described, a piece of musicis selected and reproduced from among candidate pieces of musicreproduced simultaneously or from among the candidate pieces of musicreplaced at an instruction input of “shift music forward”. However, asthe number of music data stored in the storage unit 12 increases, theremay be cases where it takes much time to reach a desired piece of musicdespite the simultaneous confirmation of a plurality of candidate music.Therefore, as will be described below, the efficiency in music selectionmay be further improved by utilizing classification informationassociated with the music data.

To put it concretely, a selected piece of music is not reproducedimmediately, but the music selection selects a category the piece ofmusic belongs to. And pieces of music belonging to the selected categoryare reproduced as new candidate pieces of music. By narrowing down thecandidate in this manner, the user can reach a final selection of musicas efficiently as when selecting the category from characterinformation, and can reach it without looking at any characterinformation. Moreover, compared with when selecting the category fromcharacter information, the user can perform the narrowing-down relyingmore on his/her senses, so that he/she has a better chance of reaching adesired piece of music even when he/she has only a hazy memory of thecategory the desired piece of music belongs to, such as performer, musicalbum name and the like.

FIG. 10 illustrates an example of classification structure of music thatcan be used in such an embodiment. As shown in FIG. 10, theclassification of music may be represented in a hierarchical structureof genre, performer, album and so forth. This classification is only anexample, and the structure may be optional; the music may be classifiedby composer instead of performer, or classification by release year maybe placed above that by album. Also, the same performer or the samealbum may be categorized into two or more groups. Information normallyattached to music data stored in the storage unit 12 can be utilized insuch classification.

The processing for music selection is carried out as follows. Thereproduction object deciding unit 28 selects a candidate piece of musicfrom each genre by firstly focusing attention on classification bygenre. Where music data as shown in FIG. 10 are stored, a piece of music“a1” belonging to “pop”, a piece of music “d1” belonging to “rock”, apiece of music “e1” belonging to “classic”, and a piece of music “f1”belonging to “jazz” are selected and reproduced simultaneously. To this,the user, while listening to the four candidate pieces of music beingreproduced, selects one of them using the input unit 18 based on thesimilarity to his/her desired piece of music or according to the mood ofthe moment.

Suppose that the piece of music “a1” is selected at this point, then thereproduction object deciding unit 28 decides that the genre of “pop” hasbeen selected. Next, a candidate piece of music from each performerbelonging to “pop” is selected In the example of FIG. 10, a piece ofmusic “a1” by performer “A” and a piece of music “b1” by performer “B”,for instance, are selected and reproduced simultaneously. And if theuser, listening to them, selects the piece of music “b1”, thereproduction object deciding unit 28 decides that performer “B” has beenselected. And next, a piece of music “b1”, a piece of music “c1” and thelike from an album “b”, an album “c” and the like, respectively, whichhave been released by performer “B” are selected and reproducedsimultaneously.

Then, if the user selects the piece of music “b1”, for instance, it willbe decided that the album “b” has been selected, and a piece of music“b1”, a piece of music “b2” and the like recorded in the album “b” willbe reproduced as candidate pieces of music. If the user selects a pieceof music at this point, then this piece of music will be decided as thefinally selected piece of music and reproduced. The arrangement may alsobe such that a selected piece of music can be determined in selectingeach hierarchical group of classification and the music selection modecan be switched to the normal mode in preparation for cases where theuser wants a piece of music reproduced in an upper hierarchical level ofclassification, such as album or performer.

It is not necessary that the classification to be used in musicselection is in a hierarchical structure as shown in FIG. 10. Forexample, the reproduction object deciding unit 28 may analyze the musicthe user has reproduced and store the information on his/her favoritetypes of music into the storage unit 12. Then the reproduction objectdeciding unit 28 can combine such preference with a classification suchas shown in FIG. 10. This will increase variation of options and allowmusic selection from a wider range of viewpoint. For example, one pieceeach of music may be extracted from the pieces of music belonging tosuch categories as “suiting user's taste and music of the same genre asthe currently selected piece”, “suiting user's taste and music of thegenre different from the currently selected piece” and “not suitinguser's taste but music of the same genre as the currently selectedpiece”, and those extracted pieces of music are reproduced as candidatepieces of music simultaneously.

With an audio reproducing apparatus 16 having features as describedabove, the user can select music while actually listening to candidatepieces of music which have been selected from various angles such as theuser's preference or reproduction history. As a result, the user may beable to reproduce a desired piece of music he/she has intended or mayhappen upon an unexpected piece of music or may arrive at an album thatagrees with the mood of the moment. In this manner, the user comesacross new discoveries which can be realized only by listening to piecesof music actually, so that the user can enjoy exploring a musical space.

FIG. 11 is a flowchart showing an operation procedure of the audioreproducing apparatus 16 with which music selection by classification asdescribed above is employed. First the reproduction object deciding unit28 detects a sign that indicates the user's desire to select music byclassification (Y of S30). More specifically, a detection is made whenthe audio reproducing apparatus 16 has started operating or when theuser has entered an instruction input to that effect to the input unit18. Note that if the user does not desire music selection byclassification (N of S30), the mode will be switched to the direct musicselection which has been explained with reference to FIG. 6 (S40).

When music selection by classification is started (Y of S30), theassigned position deciding unit 29 identifies a classification methodfor the top level in the hierarchical structure and decides thepositions to which the categories are assigned, respectively (S32). Asfor classification method for each hierarchical level, thosepredetermined may be stored in memory (not shown) which the assignedposition deciding unit 29 or the like can reference. A plurality ofpatterns of hierarchical structure may be prepared, so that the user canselect one according to his/her preference.

Then, as the reproduction object deciding unit 28 selects one each fromthe pieces of music belonging to each category, a plurality of candidatepieces of music belonging to a plurality of categories are reproduced(S34). A piece of music belonging to each category may be selected byreferring to the additive information stored together with music data inthe storage unit 12 or by referring to a hierarchical structure table ofclassification as shown in FIG. 10, which is prepared at the initialstarting of the audio reproducing apparatus 16 and stored in memory orthe like. In S34, the audio processing unit 24 assigns the sound imagesof the candidate pieces of music to their respective positions accordingto the decision of the assigned position deciding unit 29 in S32 andmakes their output.

The user selects a category by entering in the input unit 18 aninstruction input for selecting one of the candidate pieces of musicwhich he/she hears simultaneously (S36). The procedure of S32 to S36 isrepeated until the selection of a category at the bottom level in thehierarchal structure (N of S38). When the selection of the category atthe bottom level, namely, the selection of an album in the example ofFIG. 10, is completed (Y of S38), the mode is switched to the directmusic selection as shown in FIG. 6 (S40) In the example of FIG. 10, thepieces of music recorded in the album are reproduced as candidate piecesof music, and one piece of music selected from them becomes the finalselection. Note that the decision of S38 as mentioned above may be madebased on whether the user has entered an instruction input to end musicselection by classification or not, instead of whether the selection ofthe category at the bottom level has been completed or not.

According to the present embodiments heretofore described, sound imagesof a plurality of candidate audio data are assigned to differentpositions and reproduced simultaneously when the user selects a piece ofmusic therefrom. As a result, the user can make a selection of audiodata by choosing one of a plurality of outputted sounds that he/shehears simultaneously from different directions. In this music selection,the user can change the position assignment of the sound images or shiftthe positions from which the sound are heard. Thus, the user can move adesired sound to a specific position or replace candidate pieces ofmusic with new ones. This allows the user to make a music selectionintuitively while enjoying the movement of sounds. Since the user makesa selection while listening to actual sounds, there is no need forhim/her to check character information, such as titles or performers,which are attendant upon the audio data. Without the trouble of lookingat the display, selections can be made with simple operation. Moreover,even when the user only has a vague memory of character information orcannot find desired audio data readily, he/she can make selections byactually listening to sounds.

Furthermore, since the sounds of candidate audio data can be heardsimultaneously, the user can check the respective audio data in a shorttime, which results in an improved selection efficiency. Addition ofcertain processings for aural segregation of audio signals reduces thetrouble of the sounds canceling each other, thus making it easier forthe user to recognize the respective candidate sounds.

Also, constituting the input unit by an acceleration sensor fitted on anearphone or the like makes music selection possible by the orientationof the user's face. That is, the user, going through a natural movementof turning his/her face in the direction from which he/she hears adesired sound, can select the music. This not only simplifies theoperation for selection input but also reduces operation errors. Also,images corresponding to audio data being reproduced are displayed in anarrangement corresponding to the assigned positions, and the displayedarrangement is updated in linkage with the shifting of the assignedpositions. Thereby, if the user wants to visually check, the images canbe associated with the audio data intuitively based on the displayedpositions.

Also, the preferred embodiments include a mode in which audio data arenot only selected directly but also narrowed down step by step as theuser selects categories in the process. Such a mode enables the user toreach desired data efficiently even when there are a large number ofaudio data stored in the storage unit. Furthermore, the user canactually listen to the sounds of audio data belonging to a variety ofcategories, and therefore he/she can find an amusement in zapping audiodata and making unexpected or new discoveries.

The present invention has been described in conjunction with theembodiments. These embodiments are given solely by way of illustration.It will be understood by those skilled in the art that variousmodifications to the combination of each component and each processthereof are possible and that such modifications are also within thescope of the present invention.

The embodiments have been described mainly in a preferred mode in whichmusic selection is made from audio data stored in a storage unit, but itis not necessary that audio data be stored in the storage unit. Forexample, audio data may come from news programs on the radio, Internetradio programs or music contents delivered over a network or acombination thereof.

For example, a GPS (Global Positioning System) may be mounted on theaudio reproducing apparatus. Then the user can receive music or aprogram of great relevance to the location where he/she is now walkingas a candidate piece of audio data, in addition to the audio data storedin the storage unit. Thus, the sound images of all the data are assignedto different positions so that the user can select one from them bylistening to them simultaneously. In this modification, the audioreproducing apparatus may further obtain user's walking speed anddirection, using the GPS function, and shift the assigned position ofsuch data at the same speed and in the opposite direction. Then the usercan experience an illusion that the source of the sounds is fixed at acertain location in town and he/she is passing there.

An arrangement like this can save the user from the annoyance ofunwanted contents or sounds from the radio or the like following him/heraround and thus let him/her take them as general noises of town.However, if he/she happens to like the content, the user may choose itby walking closer to the source of the sound. The operation of the audioreproducing apparatus in this application is the same as that describedin the foregoing embodiments in which an acceleration sensor is used asan input means.

Also, in the foregoing embodiments, a description has been given of amode in which a candidate piece of music is replaced by another when theassigned positions for candidate pieces of music are shifted at aninstruction input of “shift music forward”. However, the number ofpieces of music to be replaced may be more than one; for example, allthe candidate pieces of music may be replaced with others. Thearrangement in such a case may be such that the number of pieces ofmusic to be replaced increases relative to the length of time for whichthe user keeps holding down the button or the like used for aninstruction input of “shift music forward”. In this case, too, the usercan select music simply by the operation of “shift music forward” and“select finally” only. Besides, he/she can remove any unwanted piece ofmusic immediately in a manner of “fast forward”, so that the efficiencyin music selection further improves.

The shifting of assigned positions of sound images of candidate piecesof music by the input unit 18 is not limited to a forward shifting in apredetermined direction as illustrated in FIG. 4. It may be front andback or right and left replacement or any other shifting. Thearrangement may be such that the user can select any from a plurality ofshifting patterns like these.

Moreover, these embodiments may be applied to audio signals reproducedby video reproducing devices such as TV receivers. In such a case, theobjects from which selections are made are video data including audiosignals. And video thumbnails or the like of a plurality of candidatevideo data are displayed on a multiple-screen display, and at the sametime individual sound images of audio signals are assigned to differentpositions and reproduced. At this time, as with the display screen of acontroller as shown in FIG. 9, the video thumbnails are displayed atpositions corresponding to the positions assigned for the audio signals.In this manner, when a TV program is to be selected from themulti-screen display, the user can make the selection by listening toaudio output at the same time.

Or, irrespective of whether the multi-screen display is made with the TVreceiver or the like or not, it may be so arranged that audio signalsfrom programs on other channels, which are so-called counterprograms,are also reproduced simultaneously with the display of a main program.In such a case, the sound image of the audio signals from the mainprogram are assigned, for instance, to the front of the user and thesound images of the audio signals from one or more counterprograms tothe back, and in addition, the audio signals from the main program areso processed that they can be emphasized by the aural segregation filter44. And when the user specifies a counterprogram, the audio and videooutputs are switched so that the selected program becomes a mainprogram. In this manner, the user can aurally follow the progress ofprograms on the other channels, such as the end of a commercial break ora special development in a sports broadcast, so that he/she can watchdesired programs without visual help.

1. An audio reproducing apparatus having an interface by which to have auser select any one of a plurality of audio data, the apparatuscomprising: a reproducing unit which assigns sound images of a pluralityof audio signals reproduced from a plurality of candidate audio data todifferent spatial positions around a user, and outputs the plurality ofaudio signals simultaneously; and an input unit which specifies aselected audio data by having the user select one of a plurality ofoutputted sounds that the user hears simultaneously from differentdirections.
 2. An audio reproducing apparatus according to claim 1,wherein the input unit includes a displacement instruction input unitwhich receives an instruction input to vary a position to which each ofsound images of the audio signals is assigned, and wherein, inaccordance with the instruction input to vary, the reproduction unitassigns each of the sound images of the audio signals to a new positionand simultaneously outputs the audio signals.
 3. An audio reproducingapparatus according to claim 2, wherein, in accordance with theinstruction input to vary, the reproducing unit replaces at least partof the candidate audio data.
 4. An audio reproducing apparatus accordingto claim 2, further including a decision unit which receives aninstruction input to determine one audio signal of which sound image isassigned to a predetermined position by an operation of the displacementinstruction unit as an object to be selected.
 5. An audio reproducingapparatus according to claim 1, wherein the input unit includes adirection pointing unit which receives an input for selecting any one ofthe plurality of directions, so that one audio signal of which soundimage is assigned to a position in the selected direction is determinedto be selected.
 6. An audio reproducing apparatus according to claim 1,wherein the input unit includes a direction detector which identifies aspecified direction by detecting a motion of the user by a sensor theuser puts on, so that one audio signal of which sound image is assignedto a position in the specified direction is determined to be selected.7. An audio reproduction apparatus according to claim 1, wherein thereproducing unit further reproduces a plurality of audio data related tothe selected audio data, as new candidate audio data.
 8. An audioreproducing apparatus according to claim 1, wherein, the reproducingunit reproduces a plurality of audio data belonging to a categoryidentical to the selected audio data at a level in a hierarchicalstructure of a music classification as subsequent candidate audio data,and further reproduces audio data selected from the candidate audio dataand a plurality of audio data belonging to the category identical to theselected audio data at a lower level in the hierarchical structure asfurther subsequent candidate audio data.
 9. An audio reproducingapparatus according to claim 1, wherein the reproducing unit decodes theplurality of candidate audio data, respectively, and performs aprocessing to have the user perceive an aurally separation of aplurality of decoded audio signals, on at least any of the plurality ofaudio signals.
 10. An audio reproducing apparatus according to claim 9,wherein the reproducing unit performs a processing for changing theaural perceivability level of the audio signals obtained by decodingrespective audio data according to a position to be assigned, on atleast any of the plurality of audio signals.
 11. An audio reproducingapparatus according to claim 1, wherein the reproducing unit assigns thesound images of the audio signals respectively to positions on acircumference of a circle with the user in the center.
 12. An audioreproducing apparatus according to claim 1, wherein the reproducing unitassigns the sound images of the audio signals to any of positionscorresponding to objects placed in a room user exists.
 13. An audioreproducing method, including: outputting a plurality of audio signalssimultaneously reproduced from a plurality of candidate audio data,after assigning sound images of the plurality of audio signals todifferent spatial positions around a user; receiving an input by whichthe user selects one of a plurality of outputted sounds that the userhears simultaneously from different directions; and reproducing onlyaudio data corresponding to the selected one unit of sound.
 14. An audioreproducing method according to claim 13, the receiving an inputincluding: receiving an instruction input to vary positions to whichsound images of the plurality of sounds are assigned so that a soundimage of a sound to be selected is assigned to a predetermined position;and receiving an instruction input to determine the sound of which soundimage is assigned to the predetermined position as an object to beselected.
 15. An audio reproducing method according to claim 13, whereinthe receiving an input includes receiving an input for specifying adirection, so that a sound of which sound image is assigned to aposition in the specified direction is determined to be selected.
 16. Acomputer program product, including: a module which reads out aplurality of candidate audio data from a memory and outputs theplurality of reproduced audio data simultaneously, after assigning soundimages of the plurality of reproduced audio data to different spatialpositions around a user, respectively; a module which receives an inputby which the user selects one of a plurality of outputted sounds thatthe user hears simultaneously from different directions; and a modulewhich reproduces only audio data corresponding to the selected one unitof sound.